The present invention relates to an inkjet head having excellent ink ejection properties and its manufacturing method applying preferable hardening properties and excellent adhesion properties of an adhesive agent.
A shared mode type inkjet head is provided with polarized piezoelectric elements, a channel board having ink flow path sectioned by partition walls, and a cover board bonded on the upper surface of the channel board. The partition walls are made share deformation to jet ink drops from a nozzle connected with the ink flow path and record on a recording medium such as paper and film.
As for the method for bonding the channel board and the cover board, a method in which the channel board and the cover board are superposed and pressed for adhesion after coating the cover board with an adhesive agent is commonly adopted. For the process of adhering plural members by using the adhesive agent, it is known to superpose for adhesion with another member after coating an adhesive agent on a member and making the coated adhesive agent in B-stage, in order for improving the handling properties of the member coated with the adhesive agent. It is considered effective to superpose for adhesion after coating the adhesive agent on the cover board and making the adhesive agent in B-stage, also in the case of bonding the channel board and the cover board. Incidentally, “B-stage” means the half-hardened state of an adhesive agent.
As for the bonding method of the channel board and the cover board, the inventers of the present invention dedicatedly studied the method of superposing and adhering the channel board and the cover board after making the adhesive agent coated on the cover board in B-stage, and found out that various problems are generated caused by the hardness of the adhesive agent while the boards are being superposed and the adhesion being completed.
Namely, when the channel board and the cover board are superposed and pressed for bonding, according to wettability of a metal electrode provided on the surface of the partition wall of the channel board, in cases where hardness of the adhesive agent is not appropriate, the phenomenon is generated that the adhesive agent flow out through the surface of metal electrode. Especially in cases where the metal electrode is formed by vacuum deposition, the tendency of generating the above phenomena is increased. This is because, when forming the metal electrode with vacuum evaporation, a side surface of the partition wall is positioned to be inclined against an evaporation source in order to properly form the metal electrode on the side surface of the partition wall. The metal layer formed with such an inclined deposition tends to be porous and have a columnar structure. Further the metal layer formed with vacuum deposition is very active and has characteristics of high surface wettability. In the case of using such a metal layer as the metal electrode, the adhesive agent coated on the cover board tends to flow out toward the metal electrode during the period from superposing to hardening of the adhesive agent. Since the channel structure forming the ink flow path is extremely fine and the shape of the inkjet head is complicated, the adhesive agent flew out over the channel board can not be cleaned completely even if cleaning is conducted by using organic solvent which dissolve the adhesive agent. Therefore a problem is caused that the adhesive agent flew out over the partition wall and remained on the partition wall after the cleaning causes degradation of ink jetting speed, and moreover, if too much adhesive agent flew out, the amount of adhesive agent at the adhesion area become insufficient resulting in insufficient boning, or in inability of ink jetting.
Further, when the channel board and the cover board are superposed and after that pressed for bonding, if the adhesive agent did not experience the hardness satisfying a prescribed condition, sufficient adhesion can not be obtained and adhesion failure is generated resulting in insufficient bonding, or in inability of ink jetting.
Therefore, the object of the present invention is to provide an inkjet head with excellent ink ejection performance and a manufacturing method for preventing the flow out of adhesive agent over the partition wall of the channel board during the process of bonding the channel board and the cover board.